State officials have unveiled a $250 million plan to replace all tollbooths along the Massachusetts Turnpike with electronic toll collection systems by spring 2017, allowing drivers to travel at normal highway speeds as they pay.

Toll plazas at the interchanges will eventually be torn down, most of the state’s 400 toll collectors will lose their jobs and the state will save an estimated $50 million in annual operating costs once the project is done, said transportation department spokeswoman Cyndi Roy.

Uncertainty hangs over a large portion of the project, however, as lawmakers have put off deciding whether tolls should continue west of Route 128 once debt tied to that part of the highway is paid off in January 2017.